Protection of valuable goods, products and brands has always been a key requirement of today's markets. In view of a steady increase in counterfeiting and unauthorized distribution of food products there is a need for efficient solutions for products and goods authentication. The ingredients of a counterfeit product may be different from but may also be the same as those of the genuine product (but in adulterated form or of inferior quality), which renders differentiation difficult.
Existing efforts to authenticate products include for example the addition of exogeneous small molecule markers, such as vitamins (e.g. US 2006/0035288), saccharides (e.g. WO 2008/002987), visually detectable markers e.g. by fluorescence, using dyes (e.g. U.S. Pat. No. 6,312,958, US 2004/0029295, EP 0 327 163, U.S. Pat. No. 4,764,290), tracers based on nitrogen- and/or sulphur-containing heterocycles (e.g. WO 2009/040563), or nucleic acids (e.g. WO 96/17954). Other approaches include the identification of geographically dependent indicators (e.g. distribution of isotopes) and indicators influenced by processing (e.g. copper content) (Pillonel et al, Mitt. Lebensm. Hyg. 95, 503 (2004) and references therein), or the identification of genetic markers using PCR-methods, such as genetically mobile elements including insertion sequence elements (or IS elements).
Bacterial IS elements were discovered during early investigations of gene expression in Escherichia coli and the bacteriophage lambda. They range from 800 to 2′500 bp in length and can be found in the genome of many different bacteria at numbers varying between a few and a few hundred copies per genome.
The structure of IS elements is typically characterized by the presence of inverted repeat sequences at their terminals and a gene coding for a transposase. They are capable of inserting at multiple sites in the genome or into plasmids (Mahillon et al. 1998). IS have been shown to promote the evolutionary adaptation of hosts (Nicoloffet al. 2003 et 2007, Papadopoulos et al. 1999, Schneider et al. 2004). However, various IS elements have shown different transpositional activities (Papadopoulos et al. 1999, Polzin et al. 1993). The restriction fragment length polymorphism associated with the presence of multiple IS elements proved to be suitable for strain typing of lactic acid bacteria at the infraspecies level (Petrovic et al. 2006, Ricci et al. 2006).
Applicants have discovered that highly variable IS elements that occur at unique locations in a single lactic acid bacterial strains may be used as strain-specific markers for the marking of dairy products as a rapid and efficient tool for their authentication.